Nowadays most cable television (CATV) operators provide, in addition to traditional television services, also various IP-based data services by taking advantage of the fact that the cable network provides an existing transmission path for the transmission of data signals as well. On the other hand, CATV customers typically have an in-house coaxial cable network, thus providing an existing media for an in-house local area network. The reuse of the low loss, high screening, large bandwidth home coax networks enables to install a reliable data network at low installation cost.
For utilizing the existing coaxial cabling for in-home networking, various technologies have been developed. One of these technologies is called Multimedia over Coax Alliance (MoCA). A MoCA network is established by connecting MoCA-enabled or MoCA interface devices at the cable outlets in the rooms of the subscriber premises. These MoCA interface devices implement a MoCA communication protocol which encapsulates the signals normally used by the multimedia devices within MoCA signal packets and then communicates the MoCA signal packets between other MoCA interface devices connected at other cable outlets typically at the frequency range of 1125-1525 MHz.
A starting point of CATV network design is that all downstream/upstream communication goes to/from the headend of the CATV operator. Therefore, in order to prevent interference between the cable outlets, all communication between in-house terminals has been prevented by splitters providing high isolation of approximately 30 dB within the CATV frequency range of 5-1006 MHz. However, such a high isolation is an impediment for reliable MoCA communications between the in-house terminals.
WO2010/133884 aims to solve this problem by disclosing a splitter with low isolation, typically <17 dB, in the 1125-1525 MHz range. The splitter circuit of WO2010/133884 may be usable in the case of one splitter providing connection for two in-house terminals, but offers little improvement when more than two terminals are to be attached to the home coax network. If applied for four terminals (as in the FIG. 7 of WO2010/133884), the signal path could go to 37 dB (i.e. two times 10 dB insertion loss and 17 dB isolation) between ports on either end of the four-way splitter.
Moreover, since the CATV signal path and the MoCA signal path are implemented by common components for both signal paths, the optimisation of both paths leads inevitably to compromises in the performance of the CATV splitter part, as well. Thus, the CATV performance in the CATV part of the spectrum deteriorates to 6 dB insertion loss and typically 20 dB isolation.
The splitter circuit of WO2010/133884 is very sensitive to its input load. The isolation of the two-way and the four-way splitters could increase significantly in sub-ranges of the MoCA bandwidth and impede the proper operation of the link, or at least reduce its capacity.